Long-Term Debt (Narrative) (Details) - USD ($)					3 Months Ended	12 Months Ended
	Mar. 18, 2025	Jan. 14, 2025	Jul. 01, 2024	May 22, 2024	Mar. 31, 2025	Dec. 31, 2024	Jul. 30, 2024
Debt Instrument [Line Items]
Interest rate margin					2.00%
Interest rate					6.816%	6.996%
Frontier Holdings [Member]
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity					$ 925,000,000		$ 900,000,000
Maturity date description					The maturity date of the Revolving Facility will be the earliest of (a) April 30, 2028, (b) 91 days prior to the maturity of the term loan facility, (c) unless such notes have been repaid and/or redeemed in full, the date that is 91 days prior to the stated maturity date of our 5.875% First Lien Notes due 2027, and (d) unless such notes have been repaid and/or redeemed in full, the date that is 91 days prior to the stated maturity date of our 5.000% First Lien Notes due 2028.
Securitized Financing Facility [Member]
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity					$ 0
Line of credit facility maximum borrowing capacity, future capacity upon satisfaction of certain conditions					0
Term Loan Facility [Member]
Debt Instrument [Line Items]
Aggregate principal amount					1,025,000,000.000
Term Loan Facility [Member] | SOFR [Member]
Debt Instrument [Line Items]
Interest rate margin		2.50%				3.50%
Term Loan Facility [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Interest rate margin		1.50%				2.50%
Revolving Facility [Member]
Debt Instrument [Line Items]
Prepayment exception for the funding of variable funding notes replaced with qualified securitization facility notes	$ 500,000,000
Letters of credit outstanding					169,000,000
Available borrowing capacity					756,000,000
Aggregate amount of certain additional obligations permitted to be outstanding				$ 2,500,000,000	$ 5,500,000,000
Percent of net available cash from first facilities to be applied to prepay existing term loans					40.00%
Securitization and receivables facilities received amount used in amendment clause					$ 1,915,000,000
Net available cash received from drawings, amount of commitments of variable funding notes					$ 500,000,000
Percent of net available cash from securitization and receivables facilities in excess of benchmark amount, to be applied to existing term loans					100.00%
Cap amount from amendment clause					$ 5,500,000,000
Maximum first lien leverage ratio covenant					5.25
Future maximum first lien leverage ratio covenant					4.75
Repayment of debt			$ 402,000,000
Revolving Facility [Member] | SOFR [Member]
Debt Instrument [Line Items]
Interest rate margin	2.50%					3.50%
Revolving Facility [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Interest rate margin	1.50%					2.50%
Revolving Facility [Member] | Securitized Financing Facility [Member]
Debt Instrument [Line Items]
Prepayment exception for the funding of variable funding notes replaced with qualified securitization facility notes	$ 500,000,000
Secured Fiber Network Revenue Term Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 750,000,000
Weighted average interest rate			7.40%
Repayment term			7 years
Secured Fiber Network Revenue Term Notes, Class A-2 [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 530,000,000
Interest rate			6.19%
Secured Fiber Network Revenue Term Notes, Class B [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 73,000,000
Interest rate			7.02%
Secured Fiber Network Revenue Term Notes, Class C [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 147,000,000
Interest rate			11.16%
Fiber Term Notes [Member]
Debt Instrument [Line Items]
Interest rate margin					5.00%
VFN Amendment [Member]
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity			$ 0
Line of credit facility maximum borrowing capacity, future capacity upon satisfaction of certain conditions			$ 500,000,000
DDTL Facility [Member]
Debt Instrument [Line Items]
Aggregate principal amount						$ 1,500,000,000
Maximum first lien leverage ratio covenant						6.75
Future maximum first lien leverage ratio covenant						2.00
DDTL Facility [Member] | Federal Funds Effective Rate [Member]
Debt Instrument [Line Items]
Interest rate margin						0.50%
DDTL Facility [Member] | One Month SOFR [Member]
Debt Instrument [Line Items]
Interest rate margin						1.00%
DDTL Facility [Member] | Fixed Rate Component [Member]
Debt Instrument [Line Items]
Interest rate margin						0.75%
DDTL Facility [Member] | SOFR Loan [Member]
Debt Instrument [Line Items]
Interest rate margin						1.75%
Terminating Lender, Revolving Credit Commitments [Member] | Frontier Holdings [Member]
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity							50,000,000
New Lender, Revolving Credit Commitments [Member] | Frontier Holdings [Member]
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity							$ 75,000,000
Maximum [Member] | Revolving Facility [Member]
Debt Instrument [Line Items]
Additional prepayment exception with respect to the Term Facility	$ 135,000,000
Maximum [Member] | DDTL Facility [Member]
Debt Instrument [Line Items]
Aggregate principal amount						$ 750,000,000
Long-term Line of Credit						$ 200,000,000